Does DXA support Extended Keyword Models?

Question

I am using dxa 2.2 (.net) and I created a custom Keyword Model BaseKeywordModel that extends KeywordModel. When DXA tries to map a published component that has a keyword field to a model that uses the BaseKeywordModel for its keyword property it fails.

I've identified the issue. The problem occurs in the DefaultModelBuilder class when trying to do this:

mappedValues.Add(MapKeyword((KeywordModelData) fieldValues, targetType, mappingData.Localization));

The problem here is that mappedValues is a Generic List of BaseKeywordModel and DXA tries to add a KeywordModel to the list, causing an exception.

This test method causes the same issue:

[Test]
public void ModelBuilderMappedValuesTest()
{
    var mappedValues = typeof(BaseKeywordModel).CreateGenericList();
    var kwdModel = new KeywordModel
    {
        Id = "Test",
        ExtensionData = new Dictionary<string, object>()
    };
    try
    {
        mappedValues.Add(kwdModel);
        Assert.Equals(mappedValues.Count, 1);
    }
    catch
    {
        Assert.Fail("Error adding keyword model to list of extended keyword models");
    }

}

This is the BaseKeywordModel class:

[Include("Title", "Description", "Key")]
public class BaseKeywordModel: KeywordModel    {    }

I need to be able to use my own class for Keywords and was wondering whether I am doing anything wrong or this is some kind of bug in the ModelBuilder.

It seems that by adding a Metadata Schema to the Keyword, the ModelBuilder is capable of creating the right instance of the object, i.e. BaseKeywordModel.

With that said, and kinda mimicking what the code does when there's a metadata schema associated to the keyword, instead of the code the ModelBuilder uses now:

if (keywordModelData.SchemaId == null)
{
    result = new KeywordModel
    {
        ExtensionData = keywordModelData.ExtensionData
    };
}

If it would use this code:

if (keywordModelData.SchemaId == null)
{
    result = (KeywordModel) targetType.CreateInstance();
    result.ExtensionData = keywordModelData.ExtensionData;
}

We should be able to use our own Keyword Extended Models without the need of a metadata schema. That change shouldn't cause any regression issues as the code already does its due diligence check:

if (typeof(KeywordModel).IsAssignableFrom(targetType)) { ... }

Will try to open a support ticket to see if I can get a hotfix in place. Of course, if you guys know a different way or see I am doing something wrong, please let me know.

Answer 1

The solution I mentioned in the question seems to be the answer. I have created a pull request in order to introduce the fix and potentially get hotfix out of it.

https://github.com/sdl/dxa-web-application-dotnet/pull/77